Bicycle wheel having flexible spokes

ABSTRACT

A spoked wheel is described that uses flexible spokes having a termination on each end that couple with a rim using nipples. The flexible spokes are supported mid-span by a hub flange cradle that transfers torque from the hub to the rim via two sub-spokes. The hub flange cradle determines whether a sub-spoke is tangential or radial. A plurality of spokes may be used on each side of the wheel.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of co-pending U.S. patent applicationSer. No. 12/284,905, entitled “BICYCLE WHEEL HAVING FLEXIBLE SPOKES,”filed on Sep. 26, 2008, the disclosure of which is incorporated hereinby reference in its entirety.

BACKGROUND OF THE INVENTION

The invention relates generally to a spoked wheel that includes a hub, awheel rim, and a plurality of spokes that transfer torque from the hubto the rim. More specifically, the invention relates to a spoked wheelthat uses flexible spokes.

Performance bicycle wheels are a compromise between weight, and staticand dynamic stability. While reducing weight, structural strength mustbe maintained.

The spokes of a bicycle wheel and their lacing pattern determine thestatic and dynamic stability of the wheel. This is most important inrear wheels, because the spokes couple the driving torque from the hubto the wheel rim. Torque transfer must occur with maximum efficiency tomaximize the energy exerted by a cyclist.

A typical spoked wheel has a first set of spokes under tension on oneside of the wheel, coupling the rim to a corresponding hub flange and asecond set of spokes under tension on the opposite side of the wheel,coupling the rim with a corresponding hub flange. The two hub flangesare set at an axial distance from each other. When the wheel is viewedin section, the hub, spokes, and rim approximate a triangle.

The spokes on the two sides of the wheel have a camber angle withrespect to the median plane of the wheel. The camber angles relate to awheel's dish. The angles cause the spoke tensioning to give rise toforce components in a direction parallel to the axis of the wheel.Balancing the force components keeps the rim centered in the medianplane.

A rear wheel hub carries at one end a sprocket cassette which is part ofthe bicycle transmission (drive train) and requires axial space. Thespokes set on the drive train side have camber angles that are smallerthan the camber angles of the spokes on the opposite side. This requiresthe smaller camber angle spokes be tensioned more than the opposite sidespokes that have greater camber angles in order to maintain the rimposition in the median plane of the wheel. Different spoke camber anglesmay also appear in front wheels, where the hub may be occupied by abrake disk. However, most symmetrically dished front wheels carry lessweight and do not have to deal with large torsional loads.

FIG. 1 shows a partial section view of a prior art rear bicycle wheel101. The wheel 101 comprises a hub 103, a sprocket cassette 105 coupledto the hub 103, a rim 107 and tire 109. The hub 103 is coupled to therim 107 via A (drive train) spokes and B (non-drive side) spokes. Thewheel's median plane M is orthogonal to the hub axis X midpoint. The Aspokes located at the drive train hub flange 111 have a camber angle αwith respect to the wheel's median plane M. The B spokes located at thenon-drive side hub flange 113 have a camber angle β with respect to thewheel's median plane M. α is less than β. Each spoke is tensioned with agiven tensile force. Corresponding tensile component vectors T_(A) andT_(B) are applied to opposite sides of the wheel 101. The horizontalvector components T_(AO) and T_(BO) of T_(A) and T_(B) are in adirection parallel to the axis X.

For wheels having an equal number of spokes on each side of the wheel,the horizontal vector components T_(AO) and T_(BO) must be balanced withone another. These forces maintain the rim 107 in the median plane M.However, the tensile force T_(A) must be greater than the tensile forceT_(B) due to its smaller camber angle. The ratio between the tensileforce T_(A) and T_(B) must be approximately equal to and opposite to theratio of the sines of the camber angles α and β. This template appliesto each pair of opposing spokes and as a sum with reference to the totaltensile forces of the spokes on one side and the opposite side.

Conventional spokes have at one end threads for engaging a nipple tocouple the spoke to a rim, and at the other end an elbow and a head forcoupling with a bore of a hub flange. Spokes are made of different typesof materials and may be butted, with reduced thickness of the spokes atthe center section. The nipple is used to adjust spoke tension. Thenipple is usually located at the rim end of the spoke, but may belocated at a hub flange. Spokes are usually circular in cross section,but may be flat or oval cross-sectioned to improve rotationaerodynamics.

Most bicycle wheels on single rider bicycles have 28, 32 or 36 spokes,while wheels on tandem bicycles have 40 or 48 spokes. Wheels with fewerspokes have an aerodynamic advantage as the aerodynamic drag from thespokes is reduced. However, fewer spokes results in a larger section ofthe rim being unsupported, thereby requiring stronger rims.

Conventional spoke lacing patterns that transfer torque from the hub tothe rim for driven wheels, or wheels with drum or disc brakes, typicallyrequire a tangential lacing pattern. The spokes leave the hub at anangle close to 90° (tangential) or at various angles, and usually crossother spokes to the rim.

Tangentially laced wheels transfer torque because one half of thespokes, called leading spokes, point in the direction of rotation, whilethe other half, called trailing spokes, point in the opposite direction.The leading and trailing spokes counteract each other when no torque isapplied. When forward torque is applied during acceleration, thetrailing spokes experience a higher tension while the leading spokesrelax. The opposite occurs when braking, with leading spokesexperiencing greater tension and trailing spokes relaxing. Leading andtrailing spokes allow for the transfer of force in either direction,minimizing tension changes, and due to symmetry, allows the wheel tostay true regardless of the torque applied.

Wheels which are not required to transfer significant amounts of torquefrom the hub to the rim may use radial lacing. In radial lacing, thespokes leave a hub flange at zero degrees without crossing anotherspoke. Radial lacing cannot adequately transfer torque because torque onthe hub would induce a stress in the hub flange bore, spoke elbows andnipples, and rim, increasing the likelihood of failure in any one ofthem. Radial lacing increases the stress on the hub flange since spoketension pulls straight at localized points. While radial lacing usesshorter spokes which minimize weight, it is offset by the need to use astronger hub. However, radially-laced wheels are stiffer and moreprecise than other lacing patterns.

A mix of radial and tangential lacing may be used on rear wheels withtangential lacing on the drive train side and radial lacing on theopposite side. Most of the torque is transferred by the drive train sideof the hub while the opposite side stabilizes the wheel. A wrong-way,half-radial lacing may be used, with radial lacing on the drive trainside and tangential lacing on the opposite side. This accounts for wheeldish, the drive train side spokes have greater tension and should not beburdened with transmitting drive torque. This design requires the hub totransmit torque from the drive train side to the opposite side. Manyother lacing patterns exist. However, most are for aesthetic reasons.

What is desired is a bicycle wheel that offers reduced weight whileallowing for increased performance.

SUMMARY OF THE INVENTION

The inventor has discovered that it would be desirable to have alight-weight high-performance bicycle wheel without the limitationsimposed by conventional spoke designs. Embodiments teach a wheel usingflexible spokes having a termination on each end that couple with a rimusing nipples. The flexible spokes are supported mid-span by a hubflange cradle that transfers torque from the hub to the rim via twodefined sub-spokes. The hub flange cradle determines whether a sub-spokeis tangential or radial. A plurality of spokes may be used on each sideof the wheel.

One aspect of the invention provides a bicycle wheel having flexiblespokes. Bicycle wheels according to this aspect of the invention includea wheel rim having a predefined even number of spoke couplings along aninner circumference, the wheel rim further having a surface forattachment of a bicycle tire, flexible spokes having a length defined bytwo end terminations, wherein a termination couples with a spokecoupling, and a rotatable wheel hub comprising a hub body positionedapproximately at a rotational center of the wheel rim, a left flangeseparated by a predefined axial distance along the hub body from a rightflange, the left and right flanges extend radially outward toward thewheel rim from the hub body and have a radial edge, a left flange outersurface that converges towards the wheel rim spoke couplings and a rightflange outer surface that converges towards the wheel rim spokecouplings, and means for securing a flexible spoke onto the left andright flange outer surfaces.

Another aspect of the invention provides means for securing a flexiblespoke. Securing means according to this aspect of the invention includea first cradle located on the outer surface of the left flange, and asecond cradle located on the outer surface of the right flange, eachcradle comprising a groove having two ends that open at a flange radialedge, a groove cross section configured to receive a flexible spoke, anda curve defined between the groove ends.

Another aspect of the invention provides a wheel hub for a spoked wheel.Wheel hubs according to this aspect of the invention include a hub body,a left flange separated by a predefined axial distance along the hubbody from a right flange, the left and right flanges extend radiallyfrom the hub body and have a radial edge, and a left flange outersurface that converges towards a wheel median plane which is orthogonalto a hub axis midpoint and a right flange outer surface that convergestowards the wheel median plane, and means for securing a flexible spokeonto the left and right flange outer surfaces.

The details of one or more embodiments of the invention are set forth inthe accompanying drawings and the description below. Other features,objects, and advantages of the invention will be apparent from thedescription and drawings, and from the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partial section view of a prior art rear bicycle wheel.

FIG. 2 is an exemplary flexible spoke.

FIG. 3 is a section view of the termination and nipple in FIG. 2.

FIG. 4 is an exemplary axial view of a drive train side hub flangecradle and sub-spoke geometry.

FIG. 5 is an exemplary hub.

FIG. 6 is an exemplary cradle section view.

FIG. 7 is an exemplary wheel embodiment.

DETAILED DESCRIPTION

Embodiments of the invention will be described with reference to theaccompanying drawing figures wherein like numbers represent likeelements throughout. Before embodiments of the invention are explainedin detail, it is to be understood that the invention is not limited inits application to the details of the examples set forth in thefollowing description or illustrated in the figures. The invention iscapable of other embodiments and of being practiced or carried out in avariety of applications and in various ways. Also, it is to beunderstood that the phraseology and terminology used herein is for thepurpose of description and should not be regarded as limiting. The useof “including,” “comprising,” or “having,” and variations thereof hereinis meant to encompass the items listed thereafter and equivalentsthereof as well as additional items.

The terms “connected” and “coupled” are used broadly and encompass bothdirect and indirect connecting, and coupling. Further, “connected” and“coupled” are not restricted to physical or mechanical connections orcouplings.

Embodiments of the invention teach a spoked wheel having a rim and ahub, and a plurality of flexible spokes that couple the hub to the rimbased on tensegrity. Tensegrity refers to the integrity of structures asa synergy between balanced tension and compression components. Tensionis continuous and compression is discontinuous such that continuous pullis balanced by equivalently discontinuous pushing forces. Embodimentsuse a plurality of flexible spokes on each side of a wheel and a hubhaving a corresponding number of cradles that may be located on theinner and/or outer surfaces of each hub flange.

FIG. 2 shows an exemplary flexible spoke 201. Each spoke 201 comprises acable 203, which may be of a synthetic material, and two endterminations 205. An end termination 205 includes a region with surfaceflats 207 configured to receive a tool to prevent the cable 203 fromtwisting during wheel assembly and a threaded region 209 in matchingcorrespondence with threads of a nipple 211 for coupling with a rim andfor tension adjustment. The spoke 201 cable 203 may include an externaljacket with modifications, such as a helical spiral 213, tailored toeliminate Aeolian induced resonance modes and to enhance aerodynamicproperties. Aeolian resonance, or vibration, is the result of vortexshedding that creates an alternating pressure imbalance. If an externaljacket modification is employed, a predefined region C where the spoke201 is supported by a hub flange cradle remains unmodified.

FIG. 3 shows a section view of the termination 205 and nipple 211. Eachtermination 205 has a terminal 301 having a hollow, expanding interiorcavity 303. The terminal 301 may be made from hard-coated aluminum,titanium, stainless steel, or other material compatible with the cable203. The terminal 301 may be treated to avoid galvanic corrosion, orcorrosion, for example, between metal and carbon.

For composite cables 203, the individual cable fibers pass into theterminal 301 through an aperture 304 and a high-performance resin 305 isinfused into the terminal interior cavity 303. The resin encapsulatesand bonds each individual fiber strand to each other, to the insidesurface of the cavity 303, and to a cone-shaped plug 307 made fromcompatible materials with its wider end at the terminal 301 end. Theresult after curing is a spoke 201 cable 203 end entrapped within theterminal 301. The plug 307, which may be a cone or truncated cone, useswedge mechanics to increase holding power. The terminal 301 interior 303geometry conforms to the cone-shaped plug 307 outside geometry, and astension on the cable 203 increases, the compression load of the plugincreases, gripping the individual fibers and distributing thecompressive force evenly over the full length of the fiber bundle.

Cables 203 made from high modulus fibers are typically stronger thanequivalent size wire cable and have a higher fatigue resistance oversteel cable. Depending on the fiber and construction, the core strengthmember may be designed to be 4 to 7 times lighter than the size andstrength equivalent wire cable. Each fiber type has uniquecharacteristics and may be selected depending upon the application.Fiber types include Ultra High Molecular Weight Polyethylene (UHMWPE),also known as High-Modulus Polyethylene (HMPE) or High-PerformancePolyethylene (HPPE), Liquid Crystal Polymer (LCP) fiber, Aramid,Polybenzobisoxazole (PBO), Polyester, Polyamide, and others. Syntheticcables offer greater strength-to-weight ratios, lower coefficients ofthermal expansion, and higher moduli of elasticity than conventionalsteel components.

The cable 203 fibers may be formed as parallel fiber cables, twistedstrand fiber cables, single braid fiber cables, double braid fibercables, and other configurations, depending on the strength, allowableelongation, and bending radius. The cable 203 may be coated or jacketed309 for protection. The jacket 309 may include external modifications toobviate Aeolian induced resonance and improve wheel aerodynamics.

FIG. 4 shows a hub 401 flange 403α spoke 201 cradle geometry. FIG. 5shows a hub 401 side view (without cassette) showing left and right hubflanges 403α, 403β and inner 501α, 501β, outer 503α, 503β and radialedge 505α, 505β surfaces. The complete hub 401, or various hubcomponents (body, flanges, bearing races, bearing seats, and others) maybe made from hard-coated aluminum, titanium, stainless steel, or othermaterial compatible with the cable 203. The spoke 201 terminals 205couple with nipples 211, which couple the spoke 201 to a rim at twodifferent rim locations. Each spoke 201 is supported by a hub flange403α, 403β cradle c 405, 407 at a predetermined region C. The C regioneffectively separates each spoke 201 into two sub-spokes 409 ₁, 409 ₂,409 ₃. Each sub-spoke has a predetermined geometry with respect to thehub axis X, defined by a cradle c 405, 407. As in conventional wheels,the sub-spokes 409 ₁, 409 ₂, 409 ₃ may be oriented radially,tangentially, or as a combination.

FIG. 4 shows two sub-spoke orientations. Radial lacing is defined by asub-spoke 409 ₁, 409 ₂ that enters the hub flange 403α perpendicular 411to a hub tangent. A cradle 405 may be machined, molded or forged in thehub flange 403α inner 501α or outer 503α surface. FIG. 6 shows a sectionview of a cradle. A cradle is a groove having a predefined curve, andlength with a load bearing curved surface 603 profile 601 sized inmatching correspondence with a spoke 201 cable 203, 409 ₁ diameter. Thecradle curve for two radial sub-spokes 409 ₁, 409 ₂ may be a radius. Thecradle groove 601 allows for the spoke 201 to fall into the hub flange403α during assembly, but is captured after all wheel spokes 201 aretensioned.

Each hub flange 403α, 403β has a predetermined camber angle α and β asdefined by the hub 401 width, hub flange 403α, 403β effective diameter,sub-spoke length and rim height 107 geometry. The camber angles α and βare approximately parallel with the sub-spokes and result in a hubflange 403α, 403β having a hollow cone shape and having inner 501α, 501βand outer 503α, 503β surfaces at the camber angles α and β.

For sub-spokes entering a hub flange at an angle that is notperpendicular 413 to a hub tangent, a cradle 407 may have a curve andlength defined by, for example, a Bézier curve. A Bézier curve is aparametric curve used to model smooth curves. Quadratic and cubic Béziercurves may be used and are suited for Computer Numerical Control (CNC)machining. A non-radial cradle 407 may be configured to support twonon-radial sub-spokes, or a combination of a radial sub-spoke 409 ₁ anda non-radial sub-spoke 409 ₃, or two non-radial sub-spokes. Thenon-radial sub-spokes function as leading and trailing spokes. Thenon-radial sub-spoke 409 ₃ in FIG. 4 functions as a trailing spoke.

FIG. 7 shows an exemplary rear wheel 701 comprising a hub 401, fourspokes 201 per wheel side and a rim 107. One skilled in the artrecognizes that a number of different spoke arrangements withcorresponding cradle curves and lengths may be practiced. For example, awheel may employ more spokes on the drive train side than the oppositeside and have different radial and non-radial sub-spoke arrangements.The complete wheel 701 may be laterally trued (eliminating localdeviations of the rim 107 to the left or right of center M), verticallytrued (eliminating local deviations of the wheel radius (the distancefrom the rim to the center of the hub)), and dish centered (centeringthe rim plane M between the outside ends of the hub 401). The dish maybe symmetrical on a front wheel. On a rear wheel, dish will beasymmetrical to accommodate the drive train cassette.

Two A side spokes use non-radial/radial cradle curves 407 on theexternal surface of the A side hub flange 403α (shown solid). The othertwo A side spokes use non-radial/radial cradle curves 407 on theinternal surface of the A side hub flange 403α (shown broken).Similarly, two B side spokes use non-radial/radial cradle curves 407 onthe external surface of the B side hub 401 flange 403β (shown broken)and the other two B side spokes use non-radial/radial cradle curves 407on the internal surface of the B side hub 401 flange 403β (shownbroken). Unlike conventional hub-spoke attachments which are typicallyapertures through a flange perpendicular with the hub body, and localizespoke head-elbow load at one point, the cradles c distribute spoke 201load C over the entire cradle curve length.

The exemplary wheel 701 pairs an A side sub-spoke with a B sidesub-spoke. Each pair comprises a radial and non-radial sub-spoke meetingat the rim 107 at approximately the same location. If a rim hassufficient width, or by use of a connection element (not shown), the Aside sub-spoke and B side sub-spoke may be connected to the rimsubstantially at the same point effecting a triangle vertice. Theconnection element may be configured to simultaneously tension the Aside sub-spoke/B side sub-spoke pair.

In a variant of the wheel 701, the A side hub flange 403α may be indexedclockwise or anti-clockwise with respect to the B side hub 401 flange403β, further separating the A sub-spokes from the B side sub-spokes atthe rim 107.

One or more embodiments of the present invention have been described.Nevertheless, it will be understood that various modifications may bemade without departing from the spirit and scope of the invention.Accordingly, other embodiments are within the scope of the followingclaims.

1. A bicycle wheel having flexible spokes comprising: a wheel rim havinga predefined even number of spoke couplings along an innercircumference, the wheel rim further having a surface for attachment ofa bicycle tire; flexible spokes having a length defined by two endterminations, wherein a termination couples with a spoke coupling; and arotatable wheel hub comprising: a hub body positioned approximately at arotational center of the wheel rim; a left flange separated by apredefined axial distance along the hub body from a right flange, theleft and right flanges extend radially outward toward the wheel rim fromthe hub body and have a radial edge; a left flange outer surface thatconverges towards the wheel rim spoke couplings and a right flange outersurface that converges towards the wheel rim spoke couplings; and meansfor securing a flexible spoke onto the left and right flange outersurfaces.
 2. The wheel according to claim 1 wherein means for securing aflexible spoke comprises: a first cradle located on the outer surface ofthe left flange; and a second cradle located on the outer surface of theright flange, each cradle comprising: a groove having two ends that openat a flange radial edge; a groove cross section configured to receive aflexible spoke; and a curve defined between the groove ends.
 3. Thewheel according to claim 2 wherein a cradle curve defines the geometryof a flexible spoke from a cradle groove opening to a wheel rim spokecoupling as a tangential sub-spoke or a radial sub-spoke.
 4. A bicyclewheel having flexible spokes comprising: a wheel rim having a predefinedeven number of spoke couplings along an inner circumference, the wheelrim further having a surface for attachment of a bicycle tire; flexiblespokes having a length defined by two end terminations, wherein atermination couples with a spoke coupling; and a rotatable wheel hubcomprising: a hub body positioned approximately at a rotational centerof the wheel rim; a left flange separated by a predefined axial distancealong the hub body from a right flange, the left and right flangesextend radially outward toward the wheel rim from the hub body and havea radial edge; a left flange inner surface that converges towards thewheel rim spoke couplings and a right flange inner surface thatconverges towards the wheel rim spoke couplings; and means for securinga flexible spoke onto the left and right flange inner surfaces.
 5. Thewheel according to claim 4 wherein means for securing a flexible spokecomprises: a first cradle located on the inner surface of the leftflange; and a second cradle located on the inner surface of the rightflange, each cradle comprising: a groove having two ends that open at aflange radial edge; a groove cross section configured to receive aflexible spoke; and a curve defined between the groove ends.
 6. Thewheel according to claim 5 wherein a cradle curve defines the geometryof a flexible spoke from a cradle groove opening to a wheel rim spokecoupling as a tangential sub-spoke or a radial sub-spoke.
 7. A wheel hubfor a spoked wheel comprising: a hub body; a left flange separated by apredefined axial distance along the hub body from a right flange, theleft and right flanges extend radially from the hub body and have aradial edge; and a left flange outer surface that converges towards awheel median plane which is orthogonal to a hub axis midpoint and aright flange outer surface that converges towards the wheel medianplane; and means for securing a flexible spoke onto the left and rightflange outer surfaces.
 8. The wheel hub according to claim 7 whereinmeans for securing a flexible spoke comprises: a first cradle located onthe outer surface of the left flange; and a second cradle located on theouter surface of the right flange, each cradle comprising: a groovehaving two ends that open at a flange radial edge; a groove crosssection configured to receive a flexible spoke; and a curve definedbetween the groove ends.
 9. The wheel hub according to claim 7 whereinthe left and right flanges further comprise: a left flange inner surfacethat converges towards the wheel median plane and a right flange innersurface that converges towards the wheel median plane; and means forsecuring a flexible spoke onto the left and right flange inner surfaces.10. The wheel hub according to claim 9 wherein means for securing aflexible spoke comprises: a first cradle located on the inner surface ofthe left flange; and a second cradle located on the inner surface of theright flange, each cradle comprising: a groove having two ends that openat a flange radial edge; a groove cross section configured to receive aflexible spoke; and a curve defined between the groove ends.